pkg/tsdb/elasticsearch/client/client.go: use time.Since instead of time.Now().Sub
pkg/tsdb/elasticsearch/client/client.go: use time.Since instead of time.Now().Sub

$ gometalinter --vendor --disable=all --enable=megacheck --deadline=10m ./...
pkg/tsdb/elasticsearch/client/client.go:147:13:warning: should use time.Since instead of time.Now().Sub (S1012) (megacheck)
pkg/tsdb/elasticsearch/client/client.go:190:14:warning: should use time.Since instead of time.Now().Sub (S1012) (megacheck)
pkg/tsdb/elasticsearch/client/client.go:218:13:warning: should use time.Since instead of time.Now().Sub (S1012) (megacheck)

grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana